CSS expressions were a way to set various CSS properties, like the width of page, specific page background color and border, and many other options. CSS expressions have been subsequently removed from all major browsers (except Internet Explorer versions 6 and 7), but back in the early 2000’s when they were released with Internet Explorer 5, they were a way for web development teams to help configure, customize, and arrange pages that tied together the look and feel of the website to the company’s business or brand identity.
Avoid CSS Expressions (Deprecated)
What are CSS Expressions?
Why CSS Expressions Should be Avoided
Lighthouse is an open-source tool that is used to run an audit against your web pages and provides scores and suggestions for improving page performance, accessibility, SEO, and more.
PageSpeed Insights is a tool created by Google that reports on the performance of a page on both mobile and desktop devices, and provides suggestions on how that page may be improved.